1. Field of the Invention
The present invention relates generally to a force-measuring apparatus and, more specifically, to a load-testing stand for calibrating hand-held grip dynamometers.
2. Description of the Related Art
Various hand dynamometers have been devised for determining the effects or application of loads in impact studies and medical applications over the past few years. One of the most important problems of the conventional dynamometers is that a dynamometer which is lightweight and easy to move from various places is almost impossible to find. Also, in 1994 and 1995, the American Medical Association adopted a formula for hand injury percentage of impairment using a hand-held grip dynamometer.
However, there is as yet no way to verify the accuracy of the determination of impairment, because quantifying the grip device is questionable with respect to its accuracy. The quantification of the hand-held grip dynamometer has not as yet been considered on an annual basis or on a post purchase basis for evaluating the accuracy of the grip device, because no portable, stand-alone grip device has been established as a professional standard. Once the device has left the manufacturing facility, it is presumed by industry, government agencies and small business consumers that necessary calibrations have been accurately determined and that existing dynamometers in the field will give corresponding comparative results. However, testing by an independent source such as a local Government Department of Weights and Measures is advised that no stationary position device has been available to permit a user to independently verify the accuracy of conventional dynamometers through a load bearing test as described herein.
U.S. Pat. No. 2,321,652 issued to Carliss discloses a dynamometer which resembles an old fashion weighing machine. Weights or forces are determined by a mechanical weighing scale which is interconnected to an analog lever arm by a spring loaded mechanical linkage for indicating a force reading via a graduated scale. The mechanical linkage is quite involve including a series of gears for transmitting various applied forces. The dynamometer according to the instant invention is completely different from the device taught by Carliss. In this regard, there is no requirement for mechanical linkages having complex gear systems nor is there a need for a mechanical weighing scale as taught therein.
U.S. Pat. No. 3,585,840 discloses a force generator which generates a force of constant amplitude and changing direction for calibrating force-sensing instruments. A resilient rod with a bearing surface provide on the free end of the rod is anchored to the instrument to be calibrated in a cantilevered arrangement. The difficulty with this particular design feature is the load capacity is limited due to moments generated by the applied force and exerted on the rod. Beyond a critical applied force failure cold occur in the rod in the form of fracture, bending, etc. The dynamometer according to the instant invention does not use the cantilevered principle, and subsequently is not prone to failure as a result of bending moments recited above.
U.S. Pat. No. 3,995,471 issued to Konomi et al. discloses a device for calibrating a chassis dynamometer comprising a drive wheel for driving rollers of the dynamometer. The drive wheel is carried by a frame via a spring, a fluid pressure operated jack which selectively lifts the drive wheel to disengage it for rollers. The device taught by Konomi et al. is entirely different to the instant invention in that there is no need for an actuating means for lifting driving rollers.
U.S. Pat. No. 4,090,393 issued to Kharitonov et al. discloses a method and apparatus for calibrating a dynamometer wherein a force of gradual magnitudes are applied to two separate cross beams. A checking or calibrating cross beam houses a weight which is compared to a master cross beam upon which forces of gradual magnitudes are placed for calibration. There are significant structural differences in this device and the dynamometer according to the invention. The dynamometer according to the instant invention does not require dual dynamometers to make calibrations. Secondly, the dynamometer according to the instant invention is readily adapted for easy assembly and disassembly which significantly reduces carrying weight during transport.
The Soviet Union Patent No. 1645864 issued to Ostrvnoi discloses a dynamometer which uses a similar calibration technique to that of Kharitonov et al. (See also SU 651222).
Other U.S. and Foreign patents of general relevance to the dynamometer according to the instant invention are U.S. Pat. No. 4,798,094 issued to Newhall et al. and Russian Pat. (SU 1707492). Newhall et al. in particular disclose an apparatus having hydrostatic bearings which provide centering of a piston and alignment of the piston-to-cylinder interface. The Russian patent discloses a device for static-dynamic calibration of dynamometers wherein forces within a specified frequency ranged are checked.
Other documents by Flood-Joy et al. (1985) Fess (1986), Radwin et al. (1991) and Riitta Harkonen (1993) are also of general relevance to the instant invention which suggests the need for a reliable dynamometer which yields valid measured data subsequent to calibration.
The hand-held dynamometer and assembly according to the instant invention is different from the prior and related art, in that it provides automatic calibration via load testing for a dynamometer with reduced material elements. This significantly improves portability of the device including an easy assembly and disassembly scheme as herein described.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus, a load testing stand for hand-held grip dynamometer solving the aforementioned problems is desired.